"By the year 2040, we will get about 1.5 to two times the amount of pollen that we have now," says Leonard Bielory, MD. Bielory is professor of environmental prediction at Rutgers University and attending physician at Robert Wood Johnson University Hospital, New Brunswick, N.J.

Pollen production will also start earlier and peak earlier, according to Bielory's new model.

He will present his findings at the American College of Allergy, Asthma & Immunology meeting in Anaheim, Calif., on Sunday.

Bielory can't say whether the increased pollen will mean more allergy misery. He did not study that. Instead, he used computer modeling to forecast future pollen levels.

Pollen Forecast: How It's Done

Climate and climate change have important effects on pollen production, its levels, how long it stays in the air, and its peak, Bielory says.

Factors such as temperature and precipitation can help predict the production of both tree and grass pollen, he says.

Previous studies have tried to predict climate's effect on pollen, he says. But many have plugged in just a few factors, such as temperature and precipitation.

His model goes beyond that. He also considered economic development, growth, and other factors over time.

Bielory determined the start date of the season, how long it would last, and how much pollen would be produced annually.

"What we see is that pollen will go up and up," he says.

The new predictions sound familiar to Lewis Ziska, PhD, a researcher at the U.S. Department of Agriculture. He reviewed the findings for WebMD.

"It is consistent with my own predictions -- that is, that climate change will have significant effects on aspects of plant and weed biology that will exacerbate both pollen season and pollen amounts," he says.

"Clearly the climate is changing," says Anthony Montanaro, MD, chief of the division of allergy and immunology at the Oregon Health & Science University in Portland. "Whether it is changing forever is arguable."

These findings were presented at a medical conference. They should be considered preliminary, as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.